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We all know about Mondrian and his grids, right? Or should I say right angles?

Composition with Large Red Plane, Yellow, Black, Grey and Blue, 1921

Composition with Grid 1, 1917

Composition in Red, Blue, and Yellow, 1937-42

Some words that come to mind: lines (straight, parallel, and perpendicular, not curved, zig zag, or diagonal), shapes (squares and rectangles, no circles, triangles, or rhombuses), the magic numbers of 4 (sides, angles) and 90 (degrees), and colors (primary: red, yellow, blue, and black/white).

Yes, we can take inspiration from Mondrian’s grids to make more squares and rectangles, but let’s shake it up and make a..

Trapezoid of Triangles!

See examples:




Do you notice anything distinctive about each composition? Pay attention to angles. Image 4 contains only right triangles. 5 features obtuse and acute triangles. 6 has a mix of all three types of triangles.

White construction paper background
Black construction paper, cut into thin strips
Glue sticks
Index cards (super fancy angle measurement device)

1. Students make a large trapezoid (a quadrilateral with only one pair of parallel lines), using 4 black strips on white background, cutting strips as needed. Edges should reach near edges of background, but not touching or going beyond them. Glue strips.

2. Using more strips, students divide trapezoid into 3 or 4 triangles. Do not glue.

3. Measure angles with index card. Place corner of index card at vertex of angle to be measured. If angle matches index card corner, it is a 90 degree or right angle.

If angle is larger than the index card corner, the angle is obtuse or > than 90 degrees.

If angle is smaller than the index card corner (hidden by it), the angle is acute or

4. Have students rearrange the black strips to make different configurations of 3 or 4 triangles, trying out different combinations of right, obtuse, and acute triangles, before gluing.

5. For remaining triangular divisions, design may be left to students’ artistic whims or you can assign specific types of compositions to individuals or groups. Students use remaining strips to make up a selected number of triangles.

6. Once completed, with all lines glued, have students use index cards to identify right, obtuse, and acute triangles, assigning a specific color for each type, then color accordingly.

Follow-up and Extension Activities:

• Students review making of artwork, comparing and contrasting numbers and types of triangles.

• Repeat above making process to make other polygons.